Flush bolts are used to lock one of the doors in a double door set, such as those used in hospitals and schools where wide exits are needed. The door with the flush bolt is closed first. When the other door is closed, the flush bolt locks the first door in place. When the other door is opened, the flush bolt automatically unlocks the first door, so that it can be opened, too, if desired.
The flush bolt includes a bolt head that extends from the top or bottom of the first door, and a strike that extends from the edge of the door that faces the other door when the two doors are closed. The strike is spring loaded in a strike assembly, and is depressed when the second door closes flush with the first door. The strike is similar to conventional latches that enter a door jamb, but in a flush bolt the strike is kept in the strike assembly when the door is closed, and does not enter the second door.
As the strike is pressed into the first door, the bolt head is pushed out of the door into a lock cavity in the door frame. However, the linkage between the strike and the bolt head in conventional flush bolts is fairly complex and expensive. Thus, there is a need for flush bolts having simpler construction.